A lithium-ion secondary battery excellent in a charge-discharge capacity characteristic and the like can be reduced in size and weight and has a high energy density. Thus, the lithium-ion secondary battery has been used as a power source for a portable device, as a power source for an electric bicycle, an electric car, and the like, or for backup of a commercial power source, and various proposals are being made for improvement of performance thereof.
In the lithium-ion secondary battery, lithium ions are transferred from a positive electrode side to a negative electrode side during charging. At this time, lithium may be deposited as dendrites to a peripheral portion of the negative electrode to cause a short circuit with an opposed electrode. Thus, in order to prevent this, a configuration is proposed, in which an outer peripheral portion of the positive electrode is disposed more inward than an outer peripheral portion of the negative electrode facing the positive electrode (see, for example, Patent Documents 1 and 2).
Further, in order to prevent internal leak due to falling of an active material from the peripheral portion of the electrode, a configuration is proposed, in which an insulating tape is adhered to a portion where a thickness is reduced by an inclination of a end portion of a positive electrode mixture (see, for example, Patent Document 3).